The present invention relates to a compressive force detecting sensor which is capable of detecting a compressive force at the time of physical contact with an object or a compressive force which is experieced at the time of said sensor being pinched by such object, sending an output for eliminate the compressive force while measuring the length of time during which the compressive force is applied and the magnitude thereof.
Conventionally, transporting vehicles which automatically run on the premises of a factory are installed with a compressive force detecting sensor in a bumper thereof for stopping such a vehicle the moment it collides with a person or an object and the assignee of the instant applicantion applied for patent for such invnetion and was granted with a patent in Japan.
The sensor is structured such that a pair of belt-like electrode plates are arranged in facing relation to each other with a predetermined spacing therebetween to form a belt-like tape switch. Said tape switch is accommodated in a sponge attached within the bumper and is adapted to stop the motion of the vehicle by use of a compressive force or impact at the time of its collision with a person or an object by switching on or off to bring said pair of electrode plates into contact with each other.
In the conventional compressive force detecting sensor as described in the foregoing, it is possible to detect the compressive force but not the length of time during which the compressive force is being exerted and the magnitude thereof Therefore, it is not possible to know the extent of damage resulting from the application of the compressive force.
The object of the present invention is to solve the problem as described in the foregoing and provide a compressive force detecting sensor which is capable of sending an output signal indicating the application of a compressive force and additional output signals which send the time period during which the compressive force lasts and the magnitude thereof by combining the tape swithch and the pressure responsive sensor.
In order to accomplish the above mentioned object, the compressive force detecting sensor of the invention has as a means a tape switch composed of a pair of belt-like electrode plates arranged in facing relation to each other with a predetermined spacing therebetween, said tape switch being covered with a pliable covering member therearound; a piezoelectric sensor having a cable or film-like shape laminated on said tape switch; and an outer shell of pliable material covering said tape switch and said piezoelectric sensor.
It is also preferable to further provide a mounting base for mounting said compressive force detecting sensor with said outer shell being nested thereon and it is further preferable to provide said mounting base with a ridge in a contact surface thereon for said piezoelectric sensor.